1. Field of the Invention
The present invention relates to a display device including a backlight, and more specifically to a display device including a backlight of a side light type or a combined type of a side light type and a downlight type.
2. Description of the Related Art
In a non-self-emitting display device such as a liquid crystal display, a so-called backlight is typically arranged so as to illuminate a display panel from the back surface. Examples of this backlight include: a downlight type, a side light type, and a planar light source type, and the like. Those of the side light type have been widely adopted, following trends toward slimming down and weight saving of the display.
The backlight of this side light type causes light from a light source to be incident on the side surface of a light guide plate, makes the light travel in the light guide plate by totally reflecting it while causing part of the light to be reflected on a reflection sheet fitted to the back surface of the light guide plate, and then emanates this part of light as a planar light source from the main surface to irradiate the back surface of the display panel. A cold-cathode tube has been used as a light source so far, but, in response to growing environmental awareness in recent years, a light emitting diode (LED) has been increasingly used.
FIG. 7 shows a conventional example of a backlight-equipped liquid crystal display device using an LED. FIG. 7 is a vertical sectional view of the liquid crystal display device. The liquid crystal display device (display device) of FIG. 7 includes a backlight 2 and a liquid crystal panel 1. In the backlight 2, to a lower chassis 21b of a rectangular parallelepiped shape with opening top and bottom sides, a back plate metal 26 is fitted so as to cover the bottom opening, and on the back plate metal 26, a light guide plate 22 of a rectangular parallelepiped shape is fitted. On the back surface of the light guide plate 22, a reflection sheet 24 is fitted, and to the front surface of the light guide plate 22, three optical sheets 25 are fitted. On the inner side wall of the lower chassis 21b opposing the side surface of the light guide plate 22, a plurality of LEDs (second light source) 23 are disposed. Then an upper chassis 21a formed with an opening that permits passage of light emanating from the light guide plate 22 therethrough is so fitted as to cover the top opening of the lower chassis 21b. By the upper chassis 21a and the lower chassis 21b, the back plate metal 26, the reflection plate 24, the light guide plate 22, and the optical sheets 25 are sandwiched.
On the other hand, the liquid crystal panel 1 is formed by enclosing a liquid crystal (not shown) between a pair of opposing glass substrates 11 and 12 separated from each other. The outer edge part of the glass substrate 12 extends farther outwardly than the glass substrate 11. Formed at this extending portion are a large number of electrode terminals (not shown) for applying a voltage to pixel electrodes formed on the front surface of the glass substrate 12. To the front and back surfaces of the liquid crystal panel 1, deflection plates 13a and 13b are fitted. The electrode terminals formed on the glass substrate 12 are connected, by a TAB (Tape Automated Bonding, flexible printed board) 3 fitted with an IC driver 31, to a circuit board 4 fitted on the back surface of the lower chassis 21b. 
Then the liquid crystal display is provided by mounting a peripheral edge part of the liquid crystal panel 1 on a step part 28 formed at a peripheral edge of the opening part of the upper chassis 21a of the backlight 2, putting a bezel 5 thereon, and fixing together the bezel 5 and the upper chassis 21a to thereby couple the liquid crystal panel 1 to the backlight 2.
In a liquid crystal display device with such a configuration, the LED 23 is fitted near the side surface of the light guide plate 22 and the TAB 3 is fitted so as to extend around the outer side of the LED 23. As a result, a surrounding part of the light guide plate 22 is larger outwardly, thus resulting in a wide frame portion of the liquid crystal display device.
Thus, to narrow down the frame portion of the liquid crystal display device, for example, JP-A-H08-248420 suggests directly arranging an LED on one of the glass substrates forming a liquid crystal panel. JP-A-2003-92020 suggests creating a hole in a FPC (Flexible Printed Circuit) connecting together a liquid crystal panel and a circuit board and then projecting an LED from this hole toward the side surface of a light guide plate.
However, the former method requires machining the glass substrate into a special shape, and also requires directly fitting the LED to the glass substrate, which are technically difficult. Further, the former method faces a problem of low efficiency of light incidence from the LED to the glass substrate. The latter method results in a large FPC width and also complicated wiring, thus presenting a problem of increased FPC manufacturing costs.